The present invention generally relates to a rinse tank for electronic substrates and a method for using such tank and more particularly, relates to a wafer rinse tank for rinsing semiconductor wafers after a metal etching process with deionized water and a method for using such rinse tank.
In the manufacture of semiconductor devices, a large quantity of deionized (DI) water is required to process integrated circuit wafers. The consumption of DI water increases with the size of the wafers. For instance, the consumption at least doubles in the processing of 200 mm size wafers when compared to the consumption in the processing of 150 mm size wafers. DI water is most frequently used in tanks and scrubbers for the frequent cleaning and rinsing of wafers in process. It is desirable that the surface of a wafer be cleaned by DI water after any process has been conducted on the wafer, i.e., oxide deposition, nitride deposition, SOG deposition or any other deposition or etching process. Such wafer cleaning step is accomplished by equipment that are installed either in-line or in a batch-type process.
For instance, a cassette-to-cassette wafer scrubbing system is one of the most used production systems for wafer cleaning prior to either a photoresist coating, oxidation, diffusion, metalization or CVD process. A typical automated wafer scrubber combines brush and solution scrubbing by DI water. The scrubber utilizes a hyperbolic high pressure spray of DI water with a retractable cleaning brush. A typical mechanical scrubbing process consists of rotating a brush near a wafer surface that is sprayed with a jet of high pressure DI water at a pressure between about 2,000 and about 3,000 psi. The brush does not actually contact the wafer surface, instead, an aquaplane is formed across the wafer surface which transfers momentum to the DI water. The movement of the DI water thus displaces and dislodges contaminating particles that have been deposited on the wafer surface. Contaminating particles are thus removed by a momentum transfer process. As a result, larger particles become more difficult to dislodge and remove from a wafer surface.
A typical wafer scrubbing process consists of a DI water spray step followed by a spin dry and nitrogen gas blow dry step. In a typical wafer scrubbing equipment, production rates are generally between 60 to 120 wafers per hour depending on the program length. The spinning speed of the wafer is between 500 to 10,000 rpm while under a water pressure of up to 6,000 psi.
In more recently developed wafer scrubbing systems, in-line systems are used which provide high pressure DI water scrubbing only while eliminating the possibility of wafer contamination by overloaded brushes. The water pressure in these systems range between 3,000 to 6,000 psi which are ejected from a nozzle mounted on an oscillating head. The wafer is spun when the oscillating spray is directed onto the wafer surface. After the cleaning step, wafer is dried by a pure nitrogen gas purge to promote rapid drying. After the scrubbing operation, wafers can be loaded into an in-line dehydration baking system for thorough drying. Batch-type systems are also used with DI water for cleaning, rinsing and drying prior to many IC processes. The systems can be programmed wherein wafers are loaded in cassettes before each cycle. One disadvantage of the batch system is their inability to be integrated into part of an automated wafer processing line.
In the conventional DI water cleaning systems, the basic requirements for the DI water cleaning system are that it provides a continuous supply of ultra-clean water with very low ionic content. It is believed that ionic contaminants in water, such as sodium, iron or copper when deposited onto a wafer surface can cause device degradation or failure. It is therefore desirable to eliminate all such ionic content from a DI water prior to using the water for cleaning wafers. A conventional method of measuring the ionic content in DI water is by monitoring the water resistivity. A water resistivity of 18xc3x97106 Ohm-cm or higher indicates a low ionic content in the DI water. In a conventional water purifying system, several sections which include charcoal filters, electrodialysis units and a number of resin units to demineralize the water are used for purifying the water.
Deionized water is frequently used in a wet bench process after a metal etching process has been conducted on a semiconductor wafer. When residual etchant chemical must be removed, deionized water rinse is frequently used in a wet bench process for semiconductor wafer processing in performing two major functions of a quick dump rinse (QDR) and a cascade overflow rinse. Conventionally, the two functions are carried out in separate tanks in order to produce the desirable. Major processing issues presented by the conventional dual-tank process are the particle re-deposition problem during a withdrawal step when cassettes are transported from a quick dump rinse tank to a cascade overflow tank. A second major issue is the large floor space required for accommodating two tanks.
It is therefore an object of the present invention to provide a rinse tank for rinsing electronic substrates after a chemical process that does not have the drawbacks or shortcomings of conventional rinse tanks.
It is another object of the present invention to provide a rinse tank for rinsing electronic substrates after a chemical etching process that allows three independent rinsing operations to be performed in the same tank.
It is a further object of the present invention to provide a rinse tank for rinsing electronic substrates after a chemical process that can be used in carrying out a quick dump rinse, a cascade overflow rinse and an inert gas bubbling rinse in the same tank.
It is another further object of the present invention to provide a rinse tank for rinsing electronic substrates after a chemical process that is equipped with a cavity adapted for holding means for a quick dump rinse, for a cascade overflow rinse and for an inert gas bubbling rinse in the same tank.
It is still another object of the present invention to provide a method for rinsing a substrate after an etching process which includes the steps of performing a cascade overflow rinse on a plurality of substrates while bubbling an inert gas through deionized water used for the rinse, and then performing a quick dump rinse on the plurality of substrates in the same rinse tank.
It is yet another object of the present invention to provide a method for rinsing a substrate after a metal etching process by first positioning at least one substrate cassette in a cavity of a rinse tank, and then performing a cascade overflow rinse, an inert gas bubbling rinse and a quick dump rinse on the plurality of substrates in the same cavity.
It is still another further object of the present invention to provide a wafer rinse tank for rinsing electronic wafers after a metal etching process which includes means for conducting a cascade overflow rinse, means for bubbling an inert gas through a rinse solution, and means for conducting a quick dump rinse on the plurality of wafers in the same rinse tank.
It is yet another further object of the present invention to provide a wafer rinse tank for rinsing semiconductor wafers after a metal etching process which includes a cavity i n the wafer rinse tank equipped for holding at least one wafer cassette filled with a plurality of wafers, means for conducting a cascade overflow rinse, means for bubbling a nitrogen gas through a rinse solution, and means for conducting a quick dump rinse on the plurality of wafers.
In accordance with the present invention, a rinse tank combining functions of quick dump rinse, cascade overflow and nitrogen bubbling simultaneously for rinsing electronic substrates after a chemical process and a method for using such rinse tank are disclosed.
In a preferred embodiment, a rinse tank for rinsing electronic substrates after a chemical process is provided which includes device for performing a quick dump rinse, device for performing a cascade overflow rinse and a device for inert gas bubbling.
The rinse tank for rinsing electronic substrates may further include a spray device for spraying deionized water on the electronic substrates. The device for performing quick dump rinse may further include means for spraying deionized water and means for draining deionized water. The insert gas bubbling device may further include a nitrogen gas bubbling device. The device for performing quick dump rinse, the device for performing cascade overflow rinse and the device for inert gas bubbling may be mounted in a cavity of a single rinse tank.
The present invention is further directed to a method for rinsing a substrate after an etching process which may be carried out by the operating steps of first providing a rinse tank that has a cavity contained therein, then positioning at least one cassette filled with a plurality of electronic substrates in the cavity, then performing a cascade overflow rinse on the plurality of substrates with deionized water while simultaneously bubbling an inert gas through the deionized water, and performing a quick dump rinse on the plurality of substrates.
The method for rinsing a substrate after an etching process may further include the step of spraying deionized water on the plurality of substrates between the cascade overflow rinse and the quick dump rinse. The step of spraying deionized water on the plurality of substrates may be carried out for at least one minute. The method may further include the step of positioning a wafer cassette filled with a plurality of wafers in the cavity. The method may further include the step of performing the cascade overflow rinse on the plurality of substrates with deionized water for at least one minute, and preferably for at least one and half minutes. The method may further include the step of performing the cascade overflow rinse process while simultaneously bubbling N2 through the deionized water. The method may further include the step of performing the quick dump rinse for at least one cycle, and preferably for at least two cycles. The method may further include the step of draining the deionized water from the rinse tank between the cascade overflow rinse step and the water spraying step.
In an alternate embodiment, a wafer rinse tank for rinsing wafers after a metal etching process can be provided which includes a cavity in the wafer rinse tank adapted for holding at least one wafer cassette filled with a plurality of wafers, means for conducting a cascade overflow rinse with deionized water on the plurality of wafers, means for bubbling an inert gas through the deionized water, and means for conducting a quick dump rinse on the plurality of wafers.
The wafer rinse tank for rinsing wafers after a metal etching process may further include means for spraying deionized water on the plurality of wafers between the cascade overflow rinse step and the quick dump rinse step. The means for bubbling an inert gas may be an N2 delivery tube equipped with a multiplicity of gas inlet.